1. Field of the Invention
The present invention relates to a method of remediating contaminated soil, and more particularly, to a method of remediating cyanide-contaminated soil in which cyanide-contaminated soil is remediated and cyanide in the soil is treated.
2. Description of Related Art
It is reported that cyanide is used in various applications such as mining, surface treatment for metal, production of aluminum and iron, and manufacture of agricultural pesticides, and as of 2001, 950000 tons of cyanide has been produced worldwide.
Cyanide has a bad impact on humans and the ecosystem. For example, when KCN or NaCN enters a human body through an oral route, HCN is released by gastric acid, and when HCN is absorbed into a human body such as a mucous membrane or lung, it inhibits oxygen delivery driven by hemoglobin. As a result, if more than a predetermined amount of cyanide is absorbed in the human body, difficulty in breathing or respiratory paralysis could result. As described above, cyanide has a bad impact on humans and the ecosystem, and thus an effluent standard for waste water is set lower than 0.01 mg/L according to the water quality standards, and a content of cyanide in soil is also restricted to less than 2 mg/kg by the soil environment conservation act.
However, a considerably wide range of soil is contaminated due to the leakage of cyanide from plating plants or metal treatment plants, or the disposal of cyanide-containing waste exceeding the standard. Thus, remediation of the cyanide-contaminated soil is required.
Purification of the cyanide-contaminated soil is performed using various processes such as room temperature oxidation, high temperature degradation and biological degradation. The biological degradation is highly economical since it is a low-cost process, but takes a long period of time. The high temperature degradation is applied for soil contaminated with cyanide which has a high concentration and low solubility. This process is efficient in treating the contaminated soil but should be performed at high temperature, and thus requires high cost. For this reason, it is not good for treating soil in a large scale. The room temperature oxidation is a lower cost process than the high temperature degradation, which is suitable for soil contaminated with cyanide having a low concentration that is easily degradable. However, it is not suitable for high concentration cyanide or solid-state cyanide.
In other words, the room temperature oxidation is a technique of injecting an oxidizing agent such as hydrogen peroxide or ozone into contaminated soil to degrade cyanide. It is known that the oxidizing agent such as hydrogen peroxide or ozone has a very low degradation capability to solid cyanide having a low solubility and strong acid dissociable (SAD) CN such as Fe(CN)64−. However, there are various limitations to remediating cyanide-contaminated soil using the room temperature oxidation since most of cyanide included in soil is a solid SDA-type.
There is also a problem in treating easily-degradable low-concentration cyanide. That is, an oxidizing agent injected into soil is consumed to degrade cyanide, and a significant amount of the oxidizing agent is also consumed by organic materials, manganese oxide and sulfide minerals contained in the soil. For this reason, to obtain a desirable result, a larger amount of an oxidizing agent than a substantially required amount of the oxidizing agent should be injected into contaminated soil.
Therefore, development and application of a technique capable of remediating cyanide-contaminated soil in a short time at a low cost at room temperature are needed.